A federal prosecutor has withdrawn from a massive Aryan Brotherhood of Texas case over security concerns even as investigators seek links between the violent prison gang and the murders of the Kaufman County district attorney, his wife and his top prosecutor.

Assistant U.S. Attorney Jay Hileman notified lawyers on the case in an email on Tuesday that he was off the statewide racketeering case, according to Richard O. Ely II, a Houston-based defense attorney who is representing one of the 34 defendants.

The Kaufman County district attorney’s office is part of a multi-agency task force of federal, state and local law enforcement agencies that took part in the investigations leading to the case. Hileman was the leading Texas-based federal prosecutor on the case.

State officials have warned that the gang could be planning retaliation against law enforcement. But Tuesday’s development is the first tangible sign that the Aryan Brotherhood’s threats against prosecutors are real.

Although the Aryan Brotherhood is one focus of the investigation into the Kaufman murders, no evidence has emerged publicly that ties the violent prison gang to the killings. No one was been charged or named as a suspect.

Kaufman County District Attorney Mike McLelland and his wife, Cynthia, were found shot to death in their home on Saturday. About two months earlier, felony prosecutor Mark Hasse was gunned down in a parking lot near the county courthouse.

Hileman could not be reached for comment. Angela Dodge, spokeswoman for the U.S. attorney’s office in Houston, did not confirm or deny the personnel change. She said her office will continue to work on the case with the Justice Department. Other federal officials declined to comment.

Ely said another Justice Department prosecutor from Washington, D.C., will be assigned to the case. That person will join David Karpel, an attorney with Justice Department’s organized crime and gang section. Ely and federal authorities said the defendants will continue to be prosecuted in Houston.

Ely said Hileman, whom he called a good friend, is probably concerned about his family after the killing of the DA and his wife. Attorneys who received the email said Hileman did not specify what the security concerns were.

“He’s obviously made a decision based on something,” Ely said.

Investigators in the Aryan Brotherhood case have intercepted numerous phone conversations from gang members inside jails and prisons across Texas as well as thousands of letters they have written as part of the sweeping racketeering case, according to court documents.

Other defense attorneys in the Aryan Brotherhood case described Hileman’s departure as surprising and said it’s practically unheard of for a prosecutor to drop out of a case like this.

“It’s shocking because he’s not the kind of guy that I would think that would back away from a challenge,” said Brent Mayr. “It would lead me to believe that there are some valid concerns.”

Brett Podolsky said prosecutors and defense lawyers take “serious cases with serious people.”

“If a guy is going to withdraw from a case like that, I’m sure he has a darn good reason to do it,” he said.

Adrian Almaguer said he wasn’t aware of any threats.

“He’s very professional and very knowledgeable and very good at what he does,” he said about Hileman. “I was just floored to have received that email because I didn’t know that this case had come to that.”

The Aryan Brotherhood of Texas, which has operated in and outside the Texas prison system since the 1980s, was dealt a serious blow in October with the federal racketeering indictments of 34 alleged members, including four top bosses.

One of the members arrested was a major for the Dallas area who was linked to murder, kidnapping, arson, gambling and drug distribution, according to a state gang report released Monday.

The Texas Department of Public Safety’s 2012 gang threat assessment also said the Aryan Brotherhood’s profile had increased in the state because of its large membership, “consistent level of violence” and other activities such as its willingness to work with drug cartels.

Although Kaufman County has prosecuted several Aryan Brotherhood gang members, other areas like Harris and Bexar counties have played a larger role in the investigation, records show.

The indictments quickly had authorities on alert.

In December, the Texas Department of Public Safety warned that the Aryan Brotherhood could be conducting surveillance against law enforcement officers as part of planned retaliation against those who helped secure the indictments in Houston.

Since the government’s investigation into the Aryan Brotherhood began in 2008, more than 60 defendants from across the state have been charged. And more indictments are expected.

They are accused of committing violent acts, including murder as well as drug dealing, dating to 1984. Several have already agreed to testify against fellow gang members, court records show.

James Stafford, a Houston attorney for one of the defendants, said he is friends with many prosecutors. He said he is sorry that some were assigned security details for them and their families as a result of what happened in Kaufman County.

“It’s a whole new experience for everybody,” he said.

Stafford said he’s not sure why the government made the Aryan Brotherhood a priority. There are many other crimes, such as Medicaid fraud, that have more of an effect on the lives of regular people, he said. The Aryan Brotherhood members, he said, have mostly been committing violent acts against each other.

“The brotherhood hadn’t been bothering John Q. Public. They have been killing each other,” he said. “People might say they are doing society a great favor.”

Robert Kepple, executive director of the Texas District and County Attorneys Association, said prosecutors came to work Monday morning thinking about security in a way they hadn’t before.

“It’s a reminder that as prosecutors we are expected to basically go toe to toe with some of the worst people in our community,” he said. “We are not used to the feeling of going to court every day and thinking ‘Hmm, am I in danger going home?’ And thinking ‘Am I in danger from somebody that I put in prison or their friends?’”